The present invention relates to formation of a discharge path for static electricity generated in a fuel filter built in a fuel supply apparatus that is mounted in a fuel tank of a vehicle and supplies fuel to an internal combustion engine.
FIG. 7 is a sectional view showing a conventional fuel supply apparatus disclosed in the International Publication No. WO99/030027.
In the drawing, reference numeral 1 is a fuel tank, numeral 2 is an opening formed on the fuel tank 1, numeral 3 is a lid housing serving also as a flange that blocks up the opening 2 and is composed of an insulating thermoplastic resin. Numeral 4 is an electric connector formed on the lid housing 3, and numeral 5 is a fuel filter that is formed into a closed container by welding the lid housing 3 serving also as a flange to a main housing 6 made of a thermoplastic resin.
This welding is carried out through a processing method generally called hot plate welding, in which ribs to serve as partitions are formed into a plane symmetry on the main housing 6 and the lid housing 3 respectively, and after end faces of both ribs are heated by a hot plate, the hot plate is removed, and the end faces of both ribs are pressed and heat welded together. Numeral 5a is a welding face welded in this process.
Numeral 7 is a filtering element accommodated in the fuel filter 5. The filtering element 7 is composed of filter paper 7a and a support member 7b for supporting the filter paper 7a, and the support member 7b is composed of a metal or a conductive resin. Numeral 8 is a pressure regulator mounted on a communicating hole 3a for communicating to the inside of the fuel filter 5. Numeral 9 is an electric fuel pump, and an intake filter 10 is mounted on an intake port 9a of the electric fuel pump 9.
Numeral 11 is a pump holding member fitted to an engaging part provided on the main housing 6, and the electric fuel pump 9 is integrally mounted on the fuel filter 5. In this process, a discharge port 9b of the electric fuel pump 9 is coupled to an inlet 5c of the fuel filter provided on the main housing 6 through a seal member 12. Numeral 13 is an earth conductor extending from the electric connector 4 to come in contact with the support member 7b in the fuel filter 5, thereby the support member 7b is electrically connected to the outside. Numeral 14 is a current-carrying terminal for supplying a driving electric power to the electric fuel pump 9 from outside. Numeral 15 is a fuel supply pipe through which a filtered fuel is delivered to the internal combustion engine, and the fuel supply pipe 15 is integrally formed with the lid housing 3 and communicates to an outlet 5d of the fuel filter.
In such a fuel supply system, the fuel pump 9 is driven by the electric power supplied from the conductive terminal 14. The fuel pump 9 pressurizes the fuel liquid taken through the intake filter 10 and delivers the fuel liquid to the fuel filter 5, in which the filtering element 7 filters dust in the fuel liquid, and the fuel liquid is supplied to the internal combustion engine through the fuel supply pipe 15. When pressure in the fuel filter 5 exceeds a predetermined pressure, the pressure regulator 8 releases excess fuel liquid into the fuel tank, thereby stabilizing pressure of the fuel liquid delivered to the internal combustion engine.
Static electricity generated by friction with the filter paper 7a when the fuel liquid passes through the filter paper 7a of the filtering element 7 gives a bad influence upon resin members such as lid housing 3, main housing 6, etc., and therefore electric charge of the fuel liquid is collected into the conductive support member 7b and dissipated through the earth conductor 13.
In the foregoing conventional fuel supply apparatus, the main housing 6 and the lid housing 3 are welded together through hot plate welding and formed into a closed container in which the filtering element 7 is enclosed. In the hot plate welding, the end faces of the ribs of the main housing 6 and the lid housing 3 to be welded together are put in contact with a heated flat plate. When the end faces of the ribs to be welded are semi-molten, the hot flat plate (hot plate) is removed, both end faces of the ribs to be welded are pressed and welded together, and accordingly both welded rib ends are more or less compressed. It is therefore essential that an upper face of the filtering element 7 inserted in the main housing 6 before welding is lower than the end face of the welded rib of the main housing 6.
Accordingly, in the earth conductor 13 made of a metal and provided through the lid housing 3 in a fluid-tight manner, the end of the earth conductor 13 interferes with the hot plate and hinders heating the faces to be welded at the time of hot plate heating. If the end of the earth conductor 13 is set with a distance from the hot plate, the end of the earth conductor 13 does not reach the support member 7b of the filtering element 7 at the completion of welding, and this brings about a problem of contact failure. It is therefore necessary that the end of the earth conductor 13 is set with a slight distance from the face of the hot plate so as to fall within a shrinkage allowance of the welded portion in the pressing and welding process, hence a problem exists in that the welding is complicated and troublesome.
Another problem exists in that heat transferred from the hot plate to the earth conductor 13 brings about looseness at the fluid-tight seal part between the lid housing 3 and the earth conductor 13.
The present invention was made to solve the above-discussed problems and intends to improve working efficiency in hot plate welding and to ensure electrical connection between the earth conductor and a portion where interior static electricity is collected.
In a fuel supply apparatus according to the present invention, a fuel filter includes a filtering element accommodated in a housing container for filtering a fuel liquid, and a fuel pump is disposed to communicate to an inlet of the fuel filter for pressurizing and delivering the fuel liquid. The housing container includes a main housing and a lid housing both made of a thermoplastic resin, the main housing and the lid housing are heat welded together at a welding face. The filtering element includes a filtering member and a support frame having a exposed pedestal, the exposed pedestal has one face positioned at the same height as the welding face when the filtering element is accommodated in the main housing, the support frame is made of a conductive thermoplastic resin and supports the filtering member. The lid housing has a peripheral wall forming a communicating hole communicated to outside, the peripheral wall has an end face positioned at the same height as the welding face and facing to the one face of the exposed pedestal. An earth conductor is connected to the one face of the exposed pedestal through the communicating hole in the condition that the main housing and lid housing are heat welded, in which the filtering element is accommodated.
Preferably, the earth conductor is welded and connected to the one face of the exposed pedestal simultaneously with heat welding the main housing and the lid housing, under the condition that the earth conductor made of a conductive thermoplastic resin is inserted in the communicating hole.
Still preferably, the earth conductor is inserted in the communicating hole, and the earth conductor is resiliently connected to the one face of the exposed pedestal.